Magnetoelectronic devices often make use of current carrying conductive lines to generate magnetic fields that affect the devices. Such devices can include magnetic field sensors, magnetoresistive random access memory (hereinafter referred to as “MRAM”) devices, or the like, and typically utilize the orientation of a magnetization vector for device operation. In MRAM devices, for example, storing data is accomplished by applying magnetic fields and causing a magnetic material in the MRAM device to be magnetized into either of two possible memory states. The magnetic fields for writing are created by passing currents through conductive lines external to the magnetic structure or through the magnetic structures themselves.
To reduce the current needed to generate a given magnetic field, the conductive lines are often surrounded on three sides with a magnetic layer of high permeability. Such a layer is referred to as a cladding layer and it typically reduces the current needed for a given magnetic field by a factor of two or more. Therefore, a cladding layer is highly desirable for a low power MRAM, as well as a high density MRAM, since lower currents enable smaller transistors and longer conductive lines for programming.
Normally, the cladding material has a magnetic moment in one direction along an axis of the material and the bit is influenced by only the fields created by the current in the bit and digit lines during programming. However, previously known cladding structures and the process for forming the cladding material may introduce errors (sometimes referred to as soft errors) in the writing or sensing of the magnetic bits. Process steps using an etch to provide electrical contact to a bit, for example, may result in the bit top electrode extending above the surrounding dielectric material, so that a bump occurs in the cladding material subsequently placed thereon. Such a bump can produce a non-uniform magnetization state in the cladding, thereby changing the field it produces. Additionally, the cladding material structure may experience a magnetic field reversal in one or more locations due to a particularly strong external field. An external magnetic field may cause the magnetic moment in portions of the cladding material surrounding the conductive line to reverse, creating a domain wall. This domain wall, when contiguous to a bit, may also changes the field produced by the cladded line.
These changes in the uniform magnetic state of the cladding can introduce errors during programming of the MRAM cells. For example, the field produced by the cladding may be reduced, so that the total field incident to the MRAM device may be less than that required for writing which can cause programming errors. Additionally, a field may be generated by the cladding even in the absence of current in the conductor, which can also cause programming errors. A typical MRAM architecture has multiple bits that are exposed to magnetic fields when one MRAM device is programmed. These one-half selected MRAM devices are particularly sensitive to unintended programming from a remnant magnetic field due to cladding. Further, if the magnetic field from the cladding is large enough, MRAM devices may be unintentionally switched by the cladding field even in the absence of a programming current.
Accordingly, it is desirable to provide a structure and fabricating method for cladded conductive lines that are less likely to produce programming errors. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.